The fine processing with lithography using a photoresist has been conducted for the preparation of semiconductor device. Said fine processing comprises forming a thin film of a photoresist composition over a silicon wafer, irradiating active light ray such as UV light ray through a mask over which the pattern of a semiconductor device has been drawn, developing and executing the etching treatment of silicon wafer of thus obtained resist pattern as a protective film. As the integration degree of a semiconductor device has been increased in recent years, there is a tendency of shortening the wavelength of the active light ray used in the above-mentioned process from i-ray (365 nm) to KrF excimer laser (248 nm). Along this process, the influence of an irregular reflection of the active light ray and a standing wave from the substrate have become major concerns. As a method of providing solutions to such concerns, a method of providing a bottom anti-reflective coating (BARC) between the photoresist and the substrate has been extensively investigated.
As the above-mentioned bottom anti-reflective coating, an inorganic bottom anti-reflective coating comprised of titanium, titanium dioxide, titanium nitride, chromium oxide, silicon oxide nitride, or the like, and an organic bottom anti-reflective coating comprised of a light-absorbing material and a polymer compound are known. The former requires facilities such as vacuum deposition equipment, a CVD device, or a spattering device for formation of the coating. On the other hand, the latter has an advantage in that it does not require any special facilities and thus various investigations have been conducted. Examples of such investigations include an acrylic resin type bottom anti-reflective coating where a hydroxyl group provided as a crosslinking functional group and a light-absorbing group are contained in the same molecule as described in the specification of U.S. Pat. No. 5,919,599, a novolac resin type bottom anti-reflective coating where a hydroxyl group provided as a crosslinking functional group and a light-absorbing group are contained in the same molecule as described in the specification of U.S. Pat. No. 5,693,691, and so on.
The desirable physical properties for the material to be used for the organic bottom anti-reflective coating include: a high absorbance with respect to light and radiation ray; insolubility to a resist solvent (absence of intermixing with a resist layer); no diffusion of small molecule into overcoating resist from the bottom anti-reflective coating material when applied on dried with heating; large dry etching rate as compared with that of the resist; and so on. For instance, they are also described in Proc. SPIE, Vol. 3678, 800-809, Proc. SPIE, Vol. 3678, 174-185 (1999), and Proc. SPIE, Vol. 2195, 225-229 (1994).
However, in the case of an LSI pattern rule having the degree of fineness for less than 0.13 μm, the delay in wiring affects speeding-up of LSI and thus advancing high-performance of LSI with the present technology for the production has become difficult, so that progress can be hardly made in the speed-up of LSI by means of the present LSI-processing technology. Therefore, Cu is one of the wiring materials used for minimizing the delay in wiring.
A dual damascene process is a technology to be introduced for replacing Al currently used as a wiring material with Cu, for example, as described in the specification of U.S. Pat. No. 6,057,239 B. In this process, a bottom anti-reflective coating is used on a substrate having a large aspect ratio (high/diameter; irregularity) as compared with that of the substrate of the conventional wiring material Al.
In addition to the above characteristics, it is desired that the bottom anti-reflective coating for the dual damascene process has an ability of controlling the coating property of the bottom anti-reflective coating in the ground substrate at the periphery of a hole, a high absorbance with respect to light and radiation ray when a bottom anti-reflective coating is applied with a uniform film thickness is carried out, and a high degree of planarization independent of the irregular shape of the substrate. However, it is difficult to use the organic bottom anti-reflective coating material as a bottom anti-reflective coating material for the dual damascene process.
Consequently, it is conceivable that the process may use two layers of: an inorganic or organic bottom anti-reflective coating having a high absorbance with respect to that of light or radiation ray; and a gap-filling material for lithography for obtaining planarization. The gap-filling material for lithography described herein is a gap-filling material, i.e., a filler or a planarizing material. The advantage of such a process is to provide a high resolution in the step of lithography and to increase an etching selectivity with a base substrate in the step of etching. The gap-filling material for lithography planarizes the irregularities of the substrate. Simultaneously, it has a high etching rate because of containing no compound having an absorbance. Therefore, a high etching selectivity with a resist can be attained in the step of etching.
The required characteristics of the gap-filling material for lithography include an insolubility to a resist solvent (no occurrence of intermixing with a resist layer), no low-molecular substance diffused from the bottom anti-reflective coating material into a top-coat resist at the time of coating or at the time of heat-drying, a high dry etching rate as compared with that of the resist, the ability to planarize the substrate having a large aspect ratio (height/diameter; irregularity), and so on. The development of a gap-filling material for lithography that satisfies all of the above requirements has been desired.
That is, an object of the present invention is to provide a composition for forming a gap-filling material for lithography to be used in a damascene process, having an excellent property of planarizing a substrate surface having irregularities such as holes and trenches, no mixing with a resist layer, forming excellent resist pattern and large dry etching rate as compared with that of a resist, and also to provide a method of forming a resist pattern using the composition for forming gap-filling material for lithography.